Filipe Luis suffered a hamstring injury in Atletico Madrid's Champions League defeat to Chelsea.
The Brazil international completed the 90 minutes against his former club on Wednesday, but complained of discomfort in his thigh in the closing stages.
Atleti sent the full-back for tests on Thursday, with the initial indications suggesting he has a hamstring injury.
The Spanish side were beaten 2-1 at the Wanda Metropolitano, with Michy Batshuayi scoring the winner in the final minute of stoppage time.
Diego Simeone's men face Leganes in their next LaLiga fixture on Saturday.